Thermal circuit breaker



0d. 4, 1949. J, KrrMAN 2,483,645

THERMAL CIRCUIT BREAKER Filed Jan. 2, 1948 JUL/H K/TMAN @www Gttorneg Patented Oct. 4,1949

UNITED sTATEs PATENT oFFicE THERMAL CIRCUIT BREAKER Julia Kitman, Pittsburzh, Pa.

Application January 2, 1948, Serial No. 117

(Cl. 20o-116) 1 Claim.

This invention relates to an electric circuit control, and important objects and advantages thereof are to provide a circuit control of the character described, which is designed and intended to supersede a fuse plug of the conventional type commonly used in branch circuits carrying the smaller currents, which will operate automatically to break a circuit when the current strength reaches a certain predetermined value, which need not be discarded after functioning to break the circuit but may be manually reset for repeated use, which is simple in its construction and arrangement, durable and efllcient in its use, positive in its action, and comparatively economical in its manufacture.

With the foregoing and other objects in view which will appear as the description proceeds, the invention resides in the novel construction, combination and arrangement of parts herein specifically described and illustrated in the accompanying drawing, but it is to be understood that changes in the form, proportions and details of construction may be resorted to that come within the scope of the claims hereunto appended.

In the drawing wherein like numerals of reference designate corresponding parts throughout the several views:

Figure 1 is a side elevational View, partly in cross section, of the improved circuit control, with the embodied mechanism in the operative position.

Figure 2 is a similar view with the mechanism in the inoperative position.

Figure 3 is a top plan view of the device.

Referring in detail to the drawing, the improved circuit control comprises a hollow plug body I including a top cover 2, which is fixed to the plug body by cementing or in any other suitable manner. The lower exterior portion of the plug body is surrounded by a ilxed metallic thread shell 3, and the bottom 4 of the plug body carries a xed contact pin 5 disposed centrally of the bottom.

The plug body I and the top cover 2 are constructed of any suitable insulating material, and the assembly of the plug body and the top cover, together with the embodied thread shell 3 and contact pin 5, provide a plug structure which has a general contour identical to the conventional type of fuse plug, and which is designed and intended to be screwed into the conventional type of electrical socket.

A thermostatically controlled switch l is mounted in the plug body I, and comprises a pair -of vertically opposed contact members 1 and I.

- 2 The lower contact member I is carried by a contact bracket 9 which is ilxed to the contact pin 5. The upper contact member 8 is carried on the lower face of the outer end of a horizontally disposed contact bar I0. The contact bar has a tapered inner end II and is pivotally connected by a pivoting pin l2 to t'he lower end of a supporting bracket I3. The latter is secured to and depends from a supporting disk I4 which is seated upon an annular shoulder I5 formed adjacent to the upper end of the inner wall of the plug body.

A spiral compression spring I6 is connected with the supporting disk I4 and with the outer end of the contact bar I0, and normally functions to shift and hold the latter to an angular position from the horizontal to open the switch 6, as clearly shown in Figure 2. The angular shiftable movement of the contact bar is limited by a shoulder I1 formed in the supporting bracket I 3.

A push button I8, having a rounded top, is mounted for vertical movement in a centrally disposed opening I9 in the top cover 2. The push button is formed with an annular flange 20 at its lower end to limit the upward movement thereof in said opening I9. The push button is provided with an inwardly opening pocket 2| for the reception of the upper end of a spiral spring 22, the lower end of which latter is seated on the supporting disk I4 and surrounds a boss 23 fixed on said supporting disk. The action of the spring 22 normally tends to force the push button to its maximum upward position.

A thermostatically atcuated, birnetallic latch arm 24 is normally disposed vertically in the plug body I, and extends through an aperture 28, provided thereior in the supporting disk I4. The latch arm 24 has its upper end xedly secured against the iiange 20 of the push button I8, and

a tapered latching element 25 is secured against the inner side of the lower free end thereof, and normally engages the tapered end II of the con tact bar I0, for holding the latter in the horizontal position against the pull of the spring I6 to maintain the switch 6 in the closed position, as shown l in Figure 1. A flexible conductor 26 connects the conductor 21, and the thread shell l. Under normal conditions the switch 6 is always closed to maintain the circuit, by the engagement of the Contact bar Ill by the latching element 2B.

The construction of the bimetallic latch arm 24 is such that if the current strength reaches and exceeds the predetermined value, the latch arm 24 will be thermostatically actuated to release the latching element 25 from the tapered end il of the contact bar l0, whereby the latter will be shifted by the action of the spring I6 to open the switch 6 and thereby break the circuit.

To reclose the circuit, the push button Il is depressed to lower the latching element 25 so that the latter will reengage the tapered end II of the contact bar I0. Upon release of the push button, the spring 22 will elevate the again normal latch arm and cause the latching elements 25 toreengage the Contact bar and shift the latter to the normal horizontal position to close the switch 6 and thereby complete the circuit.

Due to the inherent resiliency of the latch arm 24 and to the tapered end H of the contact bar l and of the latching element 25, the reengagements of the latter with said end ll is readily effected by snap action.

By providing the push button I8 with a rounded top as shown, the former cannot be engaged and pulled in the upward direction, and thus obviates the possibility of holding a closed circuit by exerting sufficient manual pull on the push button to prevent the normal thermostatic operation of the switch 6 to break the circuit when required for safety.

The present invention provides a most efficient device of its kind, which may be cheaply manufactured, and successfully and economically employed for the purposes and in the manner herein set forth.

What I claim is:

A circuit control of the class described, comprising the combination of a hollow plug body provided with a top cover. a. thread shell surrounding the lower portion o! said body, a contact pin secured ln the bottom of said body, a shoulder formed on the interior wall of said body, a supporting disk mounted on said shoulder, a supporting bracket depending from said disk, a normally horizontally disposed contact bar having a tapered inner end pivotally connected with the lower end of said supporting bracket, a switch mounted in said body and being connected with said bar, a contact bracket connected with said pin and with said switch, a push button shiftably mounted in said cover, a spring engaging said disk and said button for normally maintaining the latter in the upward position, a bimetallic latch arm depending from said button, a conductor connecting said bar with the lower end of said latch arm, a conductor connecting the upper end of said latch arm with said shell, a tapered latching element carried at the lower end of said latch arm and normally engaging the tapered end of said bar for maintaining said switch in the closed position. said latch arm being thermostatically actuated to release said element from the tapered end of said bar, a spring connected with said disk and with said bar for shifting the latter to open said switch when said bar is released from said element, said element reengaging the tapered end of said bar to reclose said switch when said button is depressed in said cover.

JULIA KITMAN.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,431,220 Donle Oct. 10, 1922 2,320,357 Platz June 1, 1943 2,325,717 Swingle Aug. 3, 1943 

